1. Field of the Invention
The invention relates generally to display systems and, more specifically, to a method and apparatus to support a self-refreshing display device coupled to a graphics controller.
2. Description of the Related Art
Computer systems typically include some sort of display device, such as a liquid crystal display (LCD) device, coupled to a graphics controller. During normal operation, the graphics controller generates video signals that are transmitted to the display device by scanning-out pixel data from a frame buffer based on timing information generated within the graphics controller. Some recently designed display devices have a self-refresh capability, where the display device includes a local controller configured to generate video signals from a static, cached frame of digital video independently from the graphics controller. When in such a self-refresh mode, the video signals are driven by the local controller, thereby allowing portions of the graphics controller to be turned off to reduce the overall power consumption of the computer system. Once in self-refresh mode, when the image to be displayed needs to be updated, control may be transitioned back to the graphics controller to allow new video signals to be generated based on a new set of pixel data.
One drawback to shutting down portions of the graphics controller is that the operating system or applications running on the host computer system may be configured to access data objects stored in a memory associated with the graphics controller. If the graphics controller is switched off, such as when the display device is operating in a self-refresh mode, the operating system or applications may lose access to the objects stored in the graphics memory. This may cause the operating system or applications to crash.
As the foregoing illustrates, what is needed in the art is an improved technique for providing access to data object stored in a memory associated with a graphics controller.